Lithography system and method for operating a lithography system

Abstract

A lithography system comprises: a radiation source for generating radiation having a specific repetition frequency; a mirror which is movable through a tilt angle for guiding the radiation in the lithography system; a measuring device which is designed to measure the tilt angle of the mirror based on a measurement signal having a measurement-signal frequency that is greater than the repetition frequency, in order to provide a time-discrete tilt-angle signal; and an analysis unit which is designed to discard specific signal values of the provided tilt-angle signal on the basis of a signal indicating the points in time at which the radiation impinged on the mirror surface of the mirror in order to provide a corrected time-discrete tilt-angle signal, and in order to determine the position of the mirror based on the corrected time-discrete tilt-angle signal.

What is claimed is: 
     
         1 . A lithography apparatus, comprising:
 a radiation source configured to generate radiation having a repetition frequency;   a MEMS mirror configured to guide the radiation within the lithography apparatus, the MEMS mirror comprising: a mirror plate displaceable through a tilt angle; a carrier plate carrying the mirror plate; a base plate; and a flexure coupling the carrier plate and the base plate;   a photodiode configured to provide a photocurrent proportional to the radiation incident on the mirror plate;   a detection device comprising a capacitive sensor between the carrier plate and the base plate, the capacitive sensor configured to detect the tilt angle of the mirror plate based on a measurement signal having a measurement signal frequency that is greater than the repetition frequency to provide a time-discrete tilt angle signal; and   an evaluation unit configured so that, when the photocurrent at a detection time assigned to a signal value is greater than a threshold value, the evaluation unit discards the signal value of the time-discrete tilt angle signal based on a signal indicating the time of incidence of the radiation on a surface of the MEMs mirror to provide a filtered time-discrete tilt angle signal and to determine a position of the mirror based on the filtered time-discrete tilt angle signal.   
     
     
         2 . The lithography apparatus of  claim 1 , wherein the measurement signal frequency is at least twice the repetition frequency. 
     
     
         3 . The lithography apparatus of  claim 1 , wherein the evaluation unit is configured to discard signal values of the time-discrete tilt angle signal whose detection times correspond to the times of incidence of the radiation on the MEMs mirror surface based on the signal that indicates the times of incidence of the radiation on the MEMs mirror surface to provide the filtered time-discrete tilt angle signal. 
     
     
         4 . The lithography apparatus of  claim 1 , wherein the capacitive sensor is configured to measure the tilt angle of the mirror plate, and the capacitive sensor comprises with comb-shaped electrodes that are enmeshed with each other. 
     
     
         5 . The lithography apparatus of  claim 4 , wherein each comb-shaped electrode has a cutout through which the flexure is guided. 
     
     
         6 . The lithography apparatus of  claim 1 , further comprising a voltmeter configured to measure a voltage drop between the mirror plate and the base plate. 
     
     
         7 . The lithography apparatus of  claim 6 , wherein the lithography apparatus comprises a micromirror array, and the micromirror array comprises a plurality of MEMS mirrors. 
     
     
         8 . The lithography apparatus of  claim 1 , wherein the lithography apparatus comprises a micromirror array, and the micromirror array comprises a plurality of MEMS mirrors. 
     
     
         9 . The lithography apparatus of  claim 1 , wherein the lithography apparatus comprises a micromirror array, and the micromirror array comprises a plurality of MEMS mirrors and the photodiode. 
     
     
         10 . The lithography apparatus of  claim 1 , further comprising a vacuum housing housing the radiation source, the MEMs mirror, the detection device and the evaluation unit. 
     
     
         11 . The lithography apparatus of  claim 10 , further comprising a controller external to the vacuum housing, wherein:
 the controller is configured to control the radiation source based on a control signal; and   the evaluation unit is configured to discard the signal values of the time-discrete tilt angle signal based on the control signal or based on a synchronization signal derived from the control signal to provide the filtered time-discrete tilt angle signal.   
     
     
         12 . The lithography apparatus of  claim 10 , comprising an illumination system, wherein the MEMs mirror, the detection device and the evaluation unit are in the illumination system. 
     
     
         13 . The lithography apparatus of  claim 1 , wherein the radiation source comprises an EUV radiation source. 
     
     
         14 . The lithography apparatus of  claim 1 , comprising an illumination system, wherein the MEMs mirror, the detection device and the evaluation unit are in the illumination system. 
     
     
         15 . The lithography apparatus of  claim 1 , further comprising a controller, wherein:
 the controller is configured to control the radiation source based on a control signal; and   the evaluation unit is configured to discard the signal values of the time-discrete tilt angle signal based on the control signal or based on a synchronization signal derived from the control signal to provide the filtered time-discrete tilt angle signal.   
     
     
         16 . The lithography apparatus of  claim 1 , wherein:
 the measurement signal frequency is at least twice the repetition frequency; and   the evaluation unit is configured to discard signal values of the time-discrete tilt angle signal whose detection times correspond to the times of incidence of the radiation on the MEMs mirror surface based on the signal that indicates the times of incidence of the radiation on the MEMs mirror surface to provide the filtered time-discrete tilt angle signal.   
     
     
         17 . The lithography apparatus of  claim 16 , wherein the capacitive sensor is configured to measure the tilt angle of the mirror plate, and the capacitive sensor comprises with comb-shaped electrodes that are enmeshed with each other. 
     
     
         18 . The lithography apparatus of  claim 1 , wherein:
 the measurement signal frequency is at least twice the repetition frequency;   the capacitive sensor is configured to measure the tilt angle of the mirror plate; and   the capacitive sensor comprises with comb-shaped electrodes that are enmeshed with each other.   
     
     
         19 . A method, comprising:
 providing the lithography apparatus of  claim 1 ; and   using the lithography apparatus to determine a position of the MEMS mirror.   
     
     
         20 . A method of operating a lithography apparatus, the lithography apparatus comprising: a radiation source configured to generate radiation having a repetition frequency; a MEMs mirror configured to guide radiation within the lithography apparatus; a photodiode configured to provide a photocurrent proportional to the radiation incident on a mirror plate of the MEMS mirror; and a detection device configured to detect the tilt angle, the MEMS mirror comprising the mirror plate; a carrier plate carrying the mirror plate; a base plate; and a flexure coupling the carrier plate and the base plate, the base plate being displaceable through a tilt angle, the detector comprising a capacitive sensor between the carrier plate and the base plate, the method comprising:
 detecting the tilt angle of the mirror plate during the operation of the lithography apparatus based on a measurement signal received by the detection device, the measurement signal having a measurement signal frequency that is greater than the repetition frequency to provide a time-discrete tilt angle signal;   when a photocurrent at the detection time assigned to the respective signal value be greater than a predetermined threshold value, discarding the signal value of the time-discrete tilt angle signal based on a signal indicating the times of incidence of the radiation on a surface of the MEMs mirror o provide a filtered time-discrete tilt angle signal; and   determining a position of the mirror using the filtered time-discrete tilt angle signal.